1. Field of the Invention
The present general inventive concept relates to an image forming apparatus, and more particularly, to an image forming apparatus which selectively blocks lamp light of a scanning lamp to change an electric potential of a photosensitive body.
2. Description of the Related Art
An electrophotographic image forming apparatus forms an image on a printing medium through charging, exposing, developing, transferring and fixing processes. Electrophotographic image forming apparatuses include a laser printer, a photocopier, a multifunction printer, etc.
As shown in FIGS. 1 and 2, a conventional image forming apparatus 1 includes a plurality of light scanning lamps 10, developing cartridges 20C and 20K, transfer rollers 33C and 33K, and light scanning devices 43C and 43K. Here, the reference numeral 35 refers to a photosensitive body screen, and reference numerals 25K and 25C refer to cleaning blades.
The respective developing cartridges 20C and 20K include casings 24C and 24K which store cyan and black toners, respectively. The casings 24C and 24K respectively accommodate charging rollers 21C and 21K, developing rollers 22C and 22K, and photosensitive bodies 23C and 23K. The image forming apparatus 1 further includes duplicate structures for yellow and magenta developing, including developing cartridges (not shown) which store yellow and magenta toners respectively, to form a color image.
The photosensitive bodies 23C and 23K are charged by the charging rollers 21C and 21K to a predetermined surface potential. The light scanning devices 43C and 43K scan light corresponding to cyan and black image information, to a surface of the charged photosensitive bodies 23C and 23K. Thus, an electrostatic latent image is formed on the photosensitive bodies 23C and 23K corresponding to the cyan and black image information.
The electrostatic latent image is developed with cyan and black toners by the developing rollers 22C and 22K to form a visible image with the cyan and black toners on the photosensitive bodies 23C and 23K.
With the foregoing method, yellow and magenta visible images are also formed on photosensitive bodies (not shown) accommodated in yellow and magenta developing cartridges (not shown).
The yellow, magenta, cyan and black visible toner images formed on the respective photosensitive bodies are superimposed and transferred to a printing medium P moving between the photosensitive bodies and the transfer rollers, thereby forming a full color image.
The electrostatic latent image remaining on the photosensitive bodies after being transferred to the printing medium P is exposed by the light scanning lamp 10 to be erased. The light scanning lamp 10 includes a light emitting diode (LED) and emits a charge erasing light in a lengthwise direction of the respective photosensitive bodies. Japanese Patent Publication No. 2006-30856, hereby incorporated by reference, discloses a charge erasing method, and thus the detailed description thereof will be avoided here.
If a user opens a cover, power of the light scanning lamp 10 should be turned off. However, if the light scanning lamp 10 malfunctions and keeps emitting light, a user may be exposed to the light directly.
Also, the photosensitive bodies 23C and 23K of the developing cartridges 20C and 20K may be damaged due to the malfunction of the light scanning lamp 10.
Furthermore, impurities which are introduced by the open cover may be attached to the light scanning lamp 10, thereby contaminating the light scanning lamp 10.